Thank you for the opportunity to help you with your question!

For a
He+ ion, we have Z = 2 and n = 1, with a lone electron. The ionisation
energy is by definition the minimum energy required to remove the
outermost electron, which is given by

E = -Ry*(Z^2/n^2) = -13.6(4) = -54.4 eV.

Choice 2

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